Surgical procedures often require the transection of tissue for a variety of purposes. In many cases, there is a need to both transect and seal tissue at the cutting site to prevent bleeding or fluid leakage from a luminal tissue structure being operated on. Accordingly, a number of devices exist for accomplishing these tasks, including devices configured for use in open surgery and minimally invasive procedures.
Many known devices include opposed jaw members configured to clamp tissue therebetween and a translating compression/cutting element that can drive the opposed jaw members to a closed position and also transect the tissue clamped between the jaw members. Sealing can likewise be accomplished in a variety of manners, including by the application of staples on either side of the compression/cutting element or the use of radio-frequency (RF) electrical or other energy to fuse the tissue together.
The opposed jaw members of some known devices may include one or more closure tracks that are configured to receive a portion of the compression/cutting element and guide the translation thereof along the jaw members. These closure tracks generally extend parallel to one another when the jaw members are in a closed position and are often arranged to provide for a desired gap between the jaw members when in the closed position.
There can be disadvantages to such devices, however. For example, a compression/cutting member can have a poor mechanical advantage when positioned close to a pivot joint of the jaw members, thereby requiring a large amount of force to compress tissue and advance along the jaw members. The poor mechanical advantage and large required force can make operation of the device difficult for users.
Additionally, in devices where RF or other energy delivery is used to seal tissue, forcing the actuation of the device can rush the procedure and transect the tissue before enough time has elapsed to sufficiently fuse the tissue. On the other hand, simply reducing the amount of compression provided in such devices can also be disadvantageous, because insufficient compression during sealing can lead to insufficient fusing of tissue. Insufficient sealing can cause bleeding from the transected tissue or leakage from a transected internal lumen or cavity.
Accordingly, there is a need for improved instruments and methods for applying variable compression to tissue to modulate required actuation forces during cutting and sealing operations. In particular, there is a need for improved instruments and methods that can reduce a required force to actuate an instrument while maintaining a desired level of compression and promoting effective sealing of tissue.